/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.sf.freecol.server.control;

import java.io.IOException;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

import net.sf.freecol.common.networking.Connection;
import net.sf.freecol.common.networking.DOMMessage;
import net.sf.freecol.common.networking.ChatMessage;
import net.sf.freecol.common.networking.MessageHandler;
import net.sf.freecol.common.networking.NetworkRequestHandler;
import net.sf.freecol.server.FreeColServer;
import net.sf.freecol.server.model.ServerPlayer;
import net.sf.freecol.server.networking.Server;

import org.w3c.dom.Element;


/**
 * Handles the network messages.
 *
 * @see Controller
 */
public abstract class InputHandler extends FreeColServerHolder implements MessageHandler
{

    private static final Logger logger = Logger.getLogger( InputHandler.class.getName( ) );

    /**
     * The handler map provides named handlers for network requests. Each
     * handler deals with a given request type.
     */
    private final Map< String, NetworkRequestHandler > _handlerMap
            = Collections.synchronizedMap( new HashMap< String, NetworkRequestHandler >( ) );


    /**
     * The constructor to use.
     *
     * @param freeColServer The main server object.
     */
    public InputHandler( final FreeColServer freeColServer )
    {
        super( freeColServer );
        // All sub-classes are forced to implement this one
        register( "logout", ( Connection connection, Element element ) ->
                logout( connection, element ) );
        register( "disconnect", new DisconnectHandler( ) );
        register( "chat", ( Connection connection, Element element ) ->
                new ChatMessage( getGame( ), element )
                        .handle( freeColServer, connection ) );
    }

    /**
     * Register a network request handler.
     *
     * @param name The name.
     * @param handler The handler.
     */
    protected final void register( String name, NetworkRequestHandler handler )
    {
        _handlerMap.put( name, handler );
    }

    /**
     * Unregister a network request handler.
     *
     * @param name The name.
     * @param handler The handler.
     * @return True if the supplied handler was actually removed.
     */
    protected final boolean unregister( String name, NetworkRequestHandler handler )
    {
        // _handlerMap.remove(name, handler) would be better?
        return _handlerMap.remove( name ) == handler;
    }

    /**
     * Deals with incoming messages that have just been received.
     *
     * @param connection The <code>Connection</code> the message was received
     *            on.
     * @param element The root element of the message.
     * @return The reply.
     */
    @Override
    public final Element handle( Connection connection, Element element )
    {
        if ( element == null ) return null;
        String tagName = element.getTagName( );
        NetworkRequestHandler handler = _handlerMap.get( tagName );
        if ( handler != null )
        {
            try
            {
                logger.log( Level.FINEST, "Handling " + tagName );
                return handler.handle( connection, element );
            }
            catch ( Exception e )
            {
                // FIXME: should we really catch Exception? The old code did.
                logger.log( Level.WARNING, "Handler failed", e );
                sendReconnectSafely( connection );
            }
        }
        else
        {
            // Should we return an error here? The old handler returned null.
            logger.warning( "No handler installed for " + tagName );
        }
        return null;
    }

    /**
     * Send a reconnect message ignoring (but logging) IO errors.
     *
     * @param connection The connection.
     */
    private void sendReconnectSafely( Connection connection )
    {
        try
        {
            connection.send( DOMMessage.createMessage( "reconnect" ) );
        }
        catch ( IOException e )
        {
            logger.log( Level.WARNING, "Could not send reconnect message!", e );
        }
    }

    /**
     * Create a reply message with an error.
     *
     * FIXME: should this be localized (return message name)?
     *
     * @param message The error message.
     * @return An error message.
     */
    protected Element createErrorReply( String message )
    {
        return DOMMessage.createMessage( "error",
                                         "message", message );
    }

    /**
     * Handles a "logout"-message.
     *
     * @param connection The <code>Connection</code> the message was received
     *     on.
     * @param element The <code>Element</code> (root element in a
     *     DOM-parsed XML tree) that holds all the information.
     * @return The reply.
     */
    protected abstract Element logout( Connection connection, Element element );


    private class DisconnectHandler implements NetworkRequestHandler
    {

        @Override
        public Element handle( Connection connection, Element disconnectElement )
        {
            // The player should be logged out by now, but just in case:
            ServerPlayer player = getFreeColServer( ).getPlayer( connection );
            logDisconnect( connection, player );
            if ( player != null && player.isConnected( ) )
            {
                logout( connection, null );
            }
            connection.reallyClose( );
            Server server = getFreeColServer( ).getServer( );
            if ( server != null )
            {
                server.removeConnection( connection );
            }
            return null;
        }

        private void logDisconnect( Connection connection, ServerPlayer player )
        {
            logger.info( "Disconnection by: " + connection + ( ( player != null ) ? " (" + player.getName( ) + ") " : "" ) );
        }
    }
}
